Under-canopy microclimate within sand dunes in the Negev Desert

Scattered shrubs are a common phenomenon in many arid landscapes. Once established, shrubs are known to create “islands of fertility”, i.e., preferential habitats for annuals and animals. In an attempt to characterize the physical conditions prevailing under the shrub, radiation, temperatures and soil moisture (0–40 cm) following rain were measured during 1993–1995 at the shaded under-canopy (UC) and at the exposed inter-shrub habitat (EXP) of two pairs of shrubs located at the north- and south-facing slopes of dunes in the Nizzana research site, western Negev Desert, Israel. In addition, the soil organic matter (SOM) and the fine (silt and clay) content (FC) were also measured. Whereas the differences in the amounts of SOM and FC were small, daylight temperatures at UC were substantially lower (6–15 °C), subsequently resulting in extended time during which the UC habitat remained wet. Moisture was retained for up to 10.5–42.6% longer at UC in comparison to EXP, mainly explained by the shading effect. SOM was found to explain only 8.6–19.6% of the results. By shading, shrubs in the Negev Desert may thus provide relatively wetter conditions for annuals, rendering them an advantage over inter-shrub habitats at this harsh arid environment.